As is known to people skilled in related arts, an LCD device has an inherent limitation on its grey-scale response time due to some characteristics of the LCD device. When used as a display for a personal computer, a user cannot perceive a significant difference between an LCD device and a CRT device. However, when used for displaying television programs, the limitation of an LCD device on the grey-scale response time becomes profound as television programs contains almost all moving images. In other words traditional LCD televisions have a significantly inferior display effect compared to CRT televisions.
Conventionally, an LCD device contains a plurality of pixels driven by a driver circuit of the LCD device. The driver circuit contains a plurality of data drivers and gate drivers. The data drivers are connected to data lines and the gate drivers are connected to gate lines of the LCD device. An overlapping area between a data line and a gate line then defines a pixel of the LCD device. In the following a traditional method for controlling the driver circuit of an LCD device is described.
FIGS. 1A and 1B are waveform diagrams showing various control and data signals seen in traditional LCD devices. When a vertical synchronization signal appears, a brand new screen would be displayed on an LCD device line by line in a raster scan pattern. Each scan line has n pixels. FIG. 1A shows waveforms of data and control signals for input a scan line's data into data drivers according to a prior art. As shown in FIG. 1A, when a STH signal becomes active, data for a first scan line's n pixels is input sequentially one pixel a time into data drivers controlled by a horizontal clock signal. When the horizontal clock signal is on a first rising edge, a data for a first pixel is shifted into a data driver, then on a second rising edge, a data for a second pixel is shifted, and following this pattern, data for the n pixels is input into the data drivers. The data for a pixel includes digital data for the pixel's R, G, and B colors. After the data for all n pixels is input, on a rising edge of a conversion signal, the data drivers convert the R, G, and B digital data of all pixels on the first scan line into corresponding driving voltages and apply the voltages on data lines. FIG. 1B shows waveforms of data and control signal for displaying a plurality of scan lines on an LCD device according to a prior art. As shown in FIG. 1B, on a first rising edge of a vertical clock signal, a gate driver will “turn on” a first gate line by asserting a gate driving signal on the first gate line, which in turn allows the driving voltages on the data lines to be applied to all pixels of the first scan line of the LCD device. The first scan line of the LCD device is thereby displayed. Subsequent scan lines will follow a same pattern to be displayed sequentially on the LCD device.
Currently, a number of methods for enhancing a grey-scale response time of an LCD device have already been proposed. Among them a method referred to as Pseudo Impulse Drive (PID) is a more promising one. As implied by its name, the PID method simulates an impulse driving method used by a CRT device to drive an LCD device, so that a display effect of the LCD device would be close to that of a CRT device. There are three commonly known PID methods as described below.
FIGS. 2A–2C are schematic diagrams for methods simulating impulse drive according to prior arts. As shown in FIG. 2A, a picture image is composed by sequentially displaying frames 1, 2, 3, and 4. In a first PID method, all black data frames 11, 12, 13 are interposed between frames 1 and 2, frames 2 and 3, and frames 3 and 4, respectively. At their time of display the foregoing frames' corresponding backlight sources 14–20 are all at light-emitting state. In this way the first PID method achieve a simulation of the impulse drive.
As shown in FIG. 2B, a picture image is composed by sequentially displaying frames 1, 2, 3, 4, 5, 6, and 7. In a second PID method, at their time of display, frames 2, 4, and 6 have corresponding backlight sources 22, 24, and 26 all at turn-off state. On the other hand, frames 1, 3, 5, and 7 at their time of display have corresponding backlight sources 21, 23, 25, and 27 all at light-emitting state. In other words the second PID method utilizes a flashing mode to achieve a simulation of the impulse drive by alternating light-emitting and turn-off backlight sources.
As shown in FIG. 2C, a picture image is composed by sequentially displaying frames 1, 2, 3, and 4. In a third PID method, all black data frames 11, 12, 13 are interposed between frames 1 and 2, frames 2 and 3, and frames 3 and 4, respectively. In addition, at their time of display, frames 11, 12, and 13 have corresponding backlight sources 22, 24, and 26 all at turn-off state, while frames 1, 2, 3, and 4 at their time of display have corresponding backlight sources 21, 23, 25, and 27 all at light-emitting state. In other words the third PID method combines the foregoing two methods to achieve a simulation of the impulse drive.